Glass is widely used as a transparency in a variety of applications due to its superior optical qualities. For example, glass is commonly used as a glazing material or as an architectural material for buildings. Glass is also commonly used as a transparency in vehicular applications. Unfortunately, glass is a relatively dense material and is also relatively brittle such that relatively large thicknesses are required to provide sufficient strength for resisting shattering when the glass is impacted by an object such as a projectile.
In attempts to avoid the weight penalty associated with glass, transparencies may be fabricated from polymeric materials. For example, transparencies may be formed of optically transparent monolithic polymers such as acrylic which is less dense than glass and which possesses suitable optical properties. Unfortunately, acrylic is a relatively low strength material making it generally unsuitable for many applications where high impact resistance is required.
In consideration of the weight penalties associated with glass and the strength limitations associated with monolithic polymers, manufacturers have also fabricated composite transparencies using conventional fibers such as ribbon-shaped fibers embedded in a matrix. Unfortunately, conventional fibers are typically spaced apart from one another in the matrix resulting in a portion of the incident light passing through gaps between the fibers. When there is a mismatch in the refractive index of the matrix and the fibers, there is a deleterious effect on the optics of the transparency due differences in the optical path lengths of the light rays and differences in the resultant angles of the light rays depending on whether the light rays pass through the main portions of the fibers or whether the light rays pass through the side surfaces of the fibers. The consequence of the differences in the optical path lengths and resultant angles is that an object viewed through the transparency may appear blurred.
As can be seen, there exists a need in the art for a high-strength transparent composite article having a fiber configuration that provides improved optical performance with reduced optical distortion.